Price will depend on a lot of things: your mare's conformation, height, show record, and breeding as well as the stallion you choose, your specific area, and the temperament and conformation of the foal.
I disagree with myhorsesonador when she say that there is no money in breeding because there is. There will always be a market for a well bred, well conformed, usable horse. Breeding responsibly is the key to success. If you are really interested in breeding your mare I would really look at your mare, find her weaknesses and breed to a stallion that compliments her.